My chip rack is at home but I wanted to ask before I forgot, but please excuse if get something wrong.

I have someone who has the siegfried and roy chip from the mirage, they claim it is rare. Chip rack has one I believe from year 1999? It is rated an "S", however I do not have a clue what this chip looks like. I do know there is a more common one out there, but wanted to know the difference and if the claim by this person is correct.

It is a $5 denomination. Any help would be great. I purchased the chip, do not know what it looks like until it gets to me in the mail. I bought 4 chips online for $15 and one was a 10th edition golden nugget, so i figure the other chips were free and does not exactly matter what they look like.

Thanks!